CD5 and mantle cell lymphoma: The focal CD5 positivity on immunohistochemistry warrants particular vigilance, as CD5 typically serves as a marker for chronic lymphocytic leukemia and mantle cell lymphoma, though occasionally expressed in DLBCL Compared to CD5-negative DLBCL patients, de novo CD5-positive DLBCL demonstrates inferior treatment response and frequent relapses.[20]